Use induction on n to verify that (1+x+⋯+z^n=1−z^n+1)/(1−z) (for z ne 1)

granuliet1u

granuliet1u

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2022-08-17

Use induction on n to verify that 1 + x + + z n = 1 z n + 1 1 z (for z 1 ). Use this to show that if c is an n-th root of 1 and c 1, then 1 + c + + c n = 0

Answer & Explanation

Jason Petersen

Jason Petersen

Beginner2022-08-18Added 13 answers

Induction: n=1 is true 1 + z = ( 1 z ) ( 1 + z ) ( 1 z ) = 1 z 2 1 z , induction step n n + 1
1 + z + + z n + z n + 1 = 1 z n + 1 1 z + z n + 1 = 1 z n + 1 1 z + ( 1 z ) z n + 1 ( 1 z ) = 1 z n + 1 + z n + 1 z n + 2 1 z

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